When a homonuclear diatomic molecule is photodissociated to give one ground state and one electronically excited atom, the wave function of the two-atom systems must reflect an uncertainty as to which atom is excited. Consequently, the wave function of the photon for a photodetector viewing the resulting fluorescence must be written as a superposition of states. Detection of such photons is shown to give rise to an interference signal in the detector voltage at a frequency depending on the Doppler shift from the atomic recoil. Photodissociation of a random distribution of molecules gives rise to a detector voltage whose power spectral density is determined by the angular distribution of photofragments.